1. Field of the Invention
The present invention relates to a group-management control method and apparatus for an elevator system with plural elevators capable of serving plural floors, and especially to a method and apparatus suited for meeting a variety of demands of users of such an elevator system.
2. Description of the Related Art
An elevator system, which is installed in a large building, is usually provided with plural elevators to serve plural floors of the building. In such an elevator system, the plural elevators are required to operate as a whole efficiently and economically in order to improve the service to users or to save the power consumption.
In a group-management control apparatus for such an elevator system, the generation of hall calls is monitored on an on-line basis and a hall call generated at a certain floor is allotted to an adaptive elevator, which is evaluated as being most suited for serving the floor, by taking account of the overall service condition for then existing hall calls, whereby waiting times of persons, who wait the arrival of available elevators in elevator halls of respective floors, can be shortened on an average.
That is to say, when a hall call is generated in a certain floor, it is evaluated which one of the plural elevators is most suitable to serve the certain floor, and the service to the floor is assigned to an elevator evaluated as the most suitable one. The aforesaid evaluation is carried out by calculating evaluation values of all of the group-controlled elevators with respect to the hall call in accordance with a predetermined evaluation function. An elevator, which has the most desired one, e.g., maximum or minimum, of the calculated evaluation values, is selected as an adaptive one to respond the hall call.
The aforesaid evaluation function includes evaluation indexes of some kinds of control items, such as a waiting time, a riding time, a cage-load factor and so on, as components to be considered for the group-control of the elevators. Such evaluation indexes are incorporated in the evaluation function with respective variable control parameters, which can be altered in accordance with a traffic demand for the elevator system. The values of the control parameters, which can satisfy desired targets of the control items under a certain traffic demand, are provided for every traffic demand in advance by the simulation carried out on an off-line basis.
In an actual daily service operation, the values of the control parameters are at first selected in response to a traffic demand at that time. Since a traffic demand is provided as various patterns for every time zone in a day, for example, the control parameters can be selected accordingly. Upon allotment of a hall call generated during the actual daily service operation, the aforesaid evaluation is carried out in accordance with the evaluation function with the selected values of the control parameters. The hall call generated is allotted to an adaptive elevator on the basis of the evaluation result.
Further, a control parameter for a certain control item as mentioned above represents the degree of influence of the control item in an evaluation function. If, therefore, a control parameter or parameters are selected at an arbitrary value, the degree of a control item or items, which is to be considered in the evaluation function, can be adjusted.
The prior art of this kind is disclosed in the Japanese laid-open patent application JP-A-58/52162 (1983) or 58/63668 (1983), for example.
According to the prior publications as described above, the adaptive group-control of an elevator system can be realized in response to an operating state of the elevator system, unless a number of control items to be considered is large If, however, the number thereof increases, an increased number of times of the simulation is required for obtaining control parameters accordingly and therefore time to obtain appropriate parameters is elongated. As a result, there-arises a problem that it takes a long time to respond to the change in the operating state.
Further, the above said prior art usually has been provided with only a particular type of the evaluation function. This is also one of the reasons why the prior art could not quickly respond to the large change in the operating state. To improve this, another prior art as disclosed in Japanese laid-open patent application JP-A-59/223672 (1984) has been proposed.
According thereto, there are provided plural evaluation methods and a final evaluation value for every elevator is obtained synthetically by weighting the respective evaluation methods in accordance with the operating state of the elevator system. An adaptive elevator is determined on the basis of the final evaluation values thus obtained for every elevator. By providing the plural evaluation methods in advance, this prior art can be more quickly respond to the change in the operating state.
Also in this prior art, a parameter for a control item and a coefficient of weighting the plural evaluation methods are obtained by the simulation. In this prior art, a control item to be considered is a waiting time only and a procedure of the simulation for obtaining the parameter and the weighting coefficient is fixed, so that the simulation in this prior art may be made simpler than that in the prior art previously described.
If, however, the number of control items to be considered increases, the effect of shortening the time of the simulation is not clear even in this prior art, because it only discloses the case in which only one control item is considered and the procedure of the simulation is fixed. It can be sufficiently presumed that if the number of control items increases, it will become considerably troublesome and time-consuming to carry out the simulation with respect to every parameter and weighting coefficient and to determine the appropriate values thereof. Accordingly, the appropriate allotment of hall calls to adaptive elevators can not be expected to timely respond to the change in the operating state of an elevator system.